sulzer latest engine
Post on 15-Nov-2014
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DESCRIPTIONthis is the latest sulzer narine engine shall be uploading the complete manual, shortly.
NATIONAL MARITIME ACADEMY
Introducing the: Wrtsil RTflex50
RT-flex: Concept and benefitsThe Wrtsil RT-flex50 low-speed twostroke marine diesel engine: common-rail system for fuel injection. common rail system for exhaust valve actuation, and full electronic control of these engine functions instead of the traditional mechanical
Benefits: Smokeless operation at all operating speeds Lower steady running speeds, in the range of 10 15 per cent nominal speed, obtained smokelessly through sequential shut-off of injectors while continuing to run on all cylinders. Reduced running costs through reduced partload fuel consumption and longer times between overhauls
Simpler setting of the engine. The as-new running settings are automatically maintained. Reduced maintenance costs through precise volumetric fuel injection control leading to extendable times between overhauls. The common-rail system with its volumetric control gives excellent balance in engine power developed between cylinders and between cycles, with precise injection timing and equalised thermal loads
Reliability is given by long-term testing of common-rail hardware in component test rigs. Higher availability owing to the integrated monitoring functions. High availability also given by the built-in redundancy, provided by the ample capacity and duplication in the supply pumps, main delivery pipes, crank-angle sensors, electronic control units and other key elements.
At the heart of the RTflex system are quickacting Sulzer Rail Valves
Various RT-flex equipment on the half-platform of a 12RT-flex96C engine. From left to right, these include (A) the local engine control panel, (B) the automatic fine filter for servo and control oil, (C) the two electricallydriven control oil pumps and (D) the supply unit.
A C B
RT-flex common-rail systemThe common rail for fuel injection is a single-piece pipe running the length of the engine at just below the cylinder cover level. The common rail and other related pipe work are arranged beneath the top engine platform and readily accessible from above. The common rail is fed with heated fuel oil at the usual high pressure (nominally 1000 bar) ready for injection.
The supply unit for the fuel has a number of high-pressure pumps actuated by cams driven through gearing from the crankshaft. Fuel is delivered from this common rail through a separate injection control unit (ICU), mounted directly on the rail, for each engine cylinder to the standard fuel injection valves which are operated in the usual way by the high-pressure fuel oil.
Supply unit of the 7RT-flex60C with fuel pumps on the right and the servo oil pumps on the left
Close view of the fuel supply pumps showing the regulating linkage.
Using quick-acting Wrtsil rail valves, they regulate the timing of fuel injection, control the volume of fuel injected, and set the shape of the injection pattern. Each ICU serves the two fuel injection valves in its corresponding cylinder cover. Each injection valve is separately controlled so that, although they normally act in unison, they can also be programmed to operate separately as necessary.
Injection control unit (ICU) for the three fuel injection valves of one cylinder. Th e dashed line marks the separation between the control oil and the fuel oil sides.
Exhaust Valve operationThe exhaust valves are operated in the same way as in RTA engines by a hydraulic pushrod but actuating energy now comes from a servo oil rail at 200 bar pressure. The servo oil is supplied by high-pressure hydraulic pumps incorporated in the supply unit with the fuel supply pumps. The electronically-controlled actuating unit for each cylinder gives full flexibility for setting the timing of valve opening and closing.
Exhaust valve actuation and servo oil systemsThe Sulzer RT-flex system also includes exhaust valve actuation and starting air control. The exhaust valves are operated in much the same way as in existing Sulzer RTA engines with a hydraulic pushrod but with the actuating energy now coming from a servo oil rail at 200 bar pressure. The servo oil is supplied by high-pressure hydraulic pumps driven from the same gear drive as the fuel pumps.
The electronically-controlled actuating unit for each cylinder gives full flexibility for valve opening and closing patterns. This unit utilises exactly the same rail valves as are used for controlling fuel injection.
The exhaust valve drive on top of the exhaust valve spindle with the hydraulic cylinder and the air spring. The two position sensors (not visible in this view) measure the radial distance to the cone to determine the spindles vertical position.
The exhaust valve actuator with the largediameter actuator piston on the left and the hydraulic control slide on the right.
Supply unit on a Sulzer 12RT-flex96C engine with the fuel pumps in a Vee-form arrangement on the left and servo oil pumps on the righthand face of the central gear drive.
Inside a Size IV rail unit during assembly. The exhaust valve actuator (A) is mounted on the servo oil rail and the injection control unit (B) is on the fuel rail. Next to the fuel rail is the smaller control oil rail (C) and the return pipe for servo and control oil (D).A
All functions in the RT-flex system are controlled and monitored through the integrated Wrtsil WECS-9520 electronic control system. This is a modular system with a separate FCM-20 microprocessor control unit for each cylinder. An additional FCM-20 unit provides all connections to other systems such as the remote control and alarm systems.
Inside one of the electronic control units
Lower turbocharger efficiencies at part load normally result in low excess combustion air with fixed valve timing. Another important contribution to fuel economy of the RT-flex50 engines is the capability to adapt easily the injection timing to various fuel properties having a poor combustion behaviour.
Three-dimensional drawing of the inside of a rail unit for an RT-fl ex96C engine, showing the fuel rail (A), the control oil rail (B and the servo oil rail (C) with the control units for injection (D) and exhaust valve actuation (E) on top of their respective rails. Other manifold pipes are provided for oil return, fuel leakage return, and the system oil supply for the exhaust valve drives.
Electronic control units beneath the front of the rail unit of a Sulzer RT-fl ex96C engine.
RT-flex: Cleaner in the environment Exhaust gas emissions have become an
important aspect of marine diesel engines. All Wrtsil RTA and RT-flex engines as standard comply with the NOX emissions limit set by IMO in Annex VI of the MARPOL 73/78 convention. RT-flex engines, however, come comfortably below this NOX limit by virtue of their extremely wide flexibility in optimising the fuel injection and exhaust valve processes.
A visible benefit of RT-flex engines is their smokeless operation at all ship speeds. The superior combustion with the common-rail system is largely because the fuel injection pressure is maintained at the optimum level irrespective of engine speed. At very low speeds, individual fuel injectors are selectively shut off and the exhaust valve timing adapted to help to keep smoke emissions below the visible limit.
Engine structureA high structural rigidity is of major importance for the todays two-stroke engines long stroke. The design is based on stress and deformation calculations carried out by using a full three-dimensional finite-element computer model for different column designs to verify the optimum frame configuration.
A gondola-type bedplate surmounted by very rigid, A-shaped double-walled columns and cylinder block, all secured by pretensioned vertical tie rods. The whole structure is very sturdy with low stresses and high stiffness. Both bedplate and columns are welded fabrications which are also designed for minimum machining.
Lowering the crankshaft into the bedplate, 6 RT Flex - 50
side is normally from the supply unit side,
but is also possible from the receiver side of the engine, to allow for maintenance of the piston rod gland and also for inspecting piston rings. The cylinder jacket is a single-piece castiron cylinder block with a high rigidity. The cylinder liners are seated in the cylinder block, and are sufficiently robust to carry the cylinder covers without requiring a support ring. A light
sleeve is applied to upper part of each liner to form a water jacket. The tilting-pad thrust bearing is integrated in the bedplate. Owing to the use of gear wheels for the supply unit drive, the thrust bearing can be very short and very stiff, and can be carried in a closed, rigid housing.
Main Bearing Housing in bed plate
Running gearThe running gear comprises the crankshaft, connecting rods, pistons and piston rods, together with their associated bearings and piston rod glands. The crankshaft is semi-built comprising combined crank pin/web elements forged from a solid ingot and the journal pins are then shrunk into the crank webs. The main bearings have white metal shells. Each main bearing cap is held down by four
A better understanding of the main bearing loads is obtained with todays finite-element analysis and elastohydrodynamic calculation techniques as they take into account the structure around the bearing and vibration of the shaft. The FE model comprises the complete shaft and its bearings together with the surrounding structure. Boundary conditions, including the crankshaft stiffness, can thus be fed into the bearing calculation.
The crosshead bearing is designed to the same principles as for all other RTA and RT-flex engines. It also features a fullwidth